Learning and Memory Flashcards
What are the two types of memory?
Declarative - memories that can be brought to conscious awareness, i.e. facts
Procedural - not directly available to conscious awareness, i.e. skills, habits
What is immediate memory?
Sum of all sensory input currently being processed at the cortical level
Very large capacity
What is short-term memory?
Conscious attention allows information to enter short-term memory
Small capacity
What is long-term memory?
Resistant to forgetting, very large capacity
Retained through a process called consolidation
What is amnesia?
Declarative memory impairment
What is retrograde amnesia?
Loss of memories which were already formed
Results from damage to areas where long-term memories are stored
What is anterograde amnesia?
Inability to form new memories
What structures are responsible for procedural memory?
Motor system structures
Cerebellum, basal ganglia, premotor cortex
What structures are responsible for delcarative memory?
Cortical areas involved in cognitive and perception
Medial temporal lobe of limbic system, Wernicke’s area, etc.
What structures are responsible for short-term memory?
More than one structure, thought to be high level sensory/association areas
Information may also be transferred to areas within the prefrontal cortex for storage
What structures are responsible for long term memory?
High level sensory/association areas which are responsible for perception of complex stimulus properties
Lesions within these cortical areas produce specific deficits affecting both memory and perception
E..g Prosopagnosia
What is consolidation?
Formation of long-term memory through the strengthening of synaptic connections between neurons in multiple cortical areas
Requires the papez circuit
What results from bilateral damage to the medial temporal lobe?
Global anterograde amnesia
Damage includes hippocampus, entorhinal cortex, and parahippocampal gyrus
What results from bilateral damage to the medial diencephalon?
Global anterograde amnesia
Mammillary bodies, anterior thalamus
Also can be caused by damage to the dorsomedial thalamus
What results from unilateral lesions to the medial temporal or medial diencephalon?
Produces antergrade amnesia, but severity is reduced from bilateral lesions, and severity may be mild
What process is responsible for synapse strengthening/weakening?
Long-term potentiation
Long-term depression
What type of channels are present on the post-synaptic spines of pyramidal neurons?
AMPA and kainate
NMDA
How are NMDA receptors dually gated?
They require depolarization and glutamate to open fully
What occurs in the post-synaptic membrane when the glutamate synapse is activated by a single presynaptic AP?
AMPA and kainate receptors open, but NMDA receptors are not because there is not enough depolarization
What occurs with repetitive use of the synapse?
The EPSPs add up and depolarize the postsynaptic neuron sufficiently to open the NMDA receptors
This allows calcium to flow into the spine and activate calcium dependent enzymes
What are two ways the activation of calcium dependent enzymes increases the sensitivity of the postsynaptic neuron to glutamate?
Phosphorylation of AMPA/KA receptors
New AMPA/KA receptors are inserted into the membrane
What is the retrograde messenger in LTP and what is its function?
Nitric oxide
Causes enhanced glutamate release from the presynaptic terminal
How do long lasting (permanent) changes to synapse strength occur?
Production of new proteins (glutamate receptors, cytoskeletal) initiated by signals of unknown origin
Newly synthesized proteins induce the creation of new synaptic contacts
Describe long term depression
Increased postsynaptic calcium stimulation activation of phosphatases that dephosphorylates AMPA/KA receptors and causes their removal from the membrane
Thought to be controlled by a lower level of intracellular calcium than LTP
How are multiple cortical areas activated in long-term memory storage?
Neruons that interconnect these areas are strengthened due to memory formation
After the formation of the memory, activation of any one of these areas will now lead to the recall of all aspects of the memory for this person
How are declarative memories retrieved?
Initiated by reactivation of one of the cortical areas where an aspect of the memory is stored
Variable - may not reactivate all areas where the memory is stored
Sometimes incorrect
